1. Field
The present disclosure relates to optical films for reducing color shift and/or organic light-emitting display apparatuses employing the same.
2. Description of the Related Art
An organic light-emitting diode (OLED) is a self-luminescent device that includes an anode, an emission layer, and a cathode. Here, when a voltage is applied to the anode and the cathode, holes are injected from the anode into the emission layer, whereas electrons are injected from the cathode into the emission layer. Here, the holes and the electrons are recombined in the emission layer to thereby form excitons. As the excitons transit from an excited state to a ground state, light is emitted therefrom.
Because an emission material in an OLED is an organic material, the reduction of the lifespan of the OLED due to the deterioration of the organic material is a serious problem, and many techniques for resolving the reduction of the lifespan are being researched. From among these techniques, a technique using a microcavity structure may increase an intensity of light of a particular wavelength by resonating the light and emitting the light of the particular wavelength out of the microcavity structure, thereby reducing power consumption and improving color purity. In other words, in the microcavity structure, distances between anodes and cathodes are designed to respectively correspond to the representative wavelengths of red (R), green (G), and blue (G), so that only light of wavelengths corresponding thereto resonate and are emitted out of the microcavity structure, and lights of other wavelengths are weakened. As a result, lights emitted to the outside become more intense and sharp, and thus brightness and color purity are improved. Furthermore, such an increase in brightness may induce low power consumption to thus improve the lifespan of an OLED.
In such a microcavity structure, the wavelength to be amplified is determined based on a thickness of an organic light-emitting layer constituting an emission layer. Meanwhile, when an organic light-emitting device is viewed from a side, a length of a lateral light path differs from a length of a front light path. A change in the length of the light path has the same effect as a change in the thickness of the organic light-emitting layer, and thus a wavelength to be amplified is changed. In other words, as the viewing angle is titled from the front to a side, the maximum resonance wavelength becomes shorter, and thus a color shift occurs as the maximum resonance wavelength decreases. For example, even if a white color is embodied at the front, the white color may become bluish at a lateral side due to a blue shift phenomenon.